For a playgoer, “Accomplice: San Diego” promises to bring a whole new meaning to the term “plot.”

That’s because instead of following one, you’ll be a conspirator in one: a seamy criminal scheme playing out on the streets of Little Italy.

Not a real one, of course — unless things really go off-script in this deliberately unpredictable theatrical event brought to you by La Jolla Playhouse.

“Accomplice” is the latest in the theater’s “Without Walls” series of site-specific shows, and it puts participants in the service of mysterious, shady doings as they stroll around the neighborhood near downtown San Diego.

“It’s a crime story where you are aiding and abetting a series of sort of low-rent criminals from different walks of life,” explains Tom Salamon, who developed the concept about eight years ago with his sister, Betsy Salamon-Sufott.

“You’re playing the accomplice to this plot. (But) you’re just sort of playing yourself” — a dupe recruited by wrongdoers to deliver messages and generally move the whole dodge along.

The first two New York versions of “Accomplice” were much-buzzed happenings and attracted the attention of the Broadway and TV star Neil Patrick Harris, who helped produce subsequent “Accomplice” incarnations in Los Angeles and London. (He remains involved in the “Accomplice” operation.)

In the Little Italy iteration (whose plot is largely borrowed from “Accomplice: New York”), even the starting location is secret: Playgoers get that information in a phone call, before heading out in groups of 10 on a clue-seeking stroll of a mile or so. (The event is for those 21 and older only.)

Much of the fun, Salamon says, stems from the fuzzy line between what’s part of the show and what’s endemic to the urban environment. Participants might find themselves asking, is that just graffiti or some kind of clue? Is that guy in the hat an actor or a random passer-by?

“Those are the best things to happen,” he says. “The whole thing is designed to make you feel that everyone’s an extra in the story.”

What — a play that doesn’t promise to end the same way twice? There oughta be a law.